A novel ratiometric peptide-based fluorescent probe for sequential detection of Hg2+ and S2− ions and its application in living cells and zebrafish imaging

A new ratiometric peptide-based fluorescent probe DWPH was designed and synthesized, comprising dansyl fluorophore as a fluorescent dye, and tripeptide backbone (Trp-Pro-His-NH2) as a recognition group. The addition of Hg2+ caused the maximum emission peak of DWPH to blue shift from 560 nm to 510 nm. DWPH exhibited large Stokes shift (230 nm), satisfactory water solubility (100 % aqueous medium), good selectivity (only Hg2+), high sensitivity (24.6 nM), rapid response (within 50 s) and strong anti-interference ability for Hg2+ detection over a wide pH range (7–11). Additionally, the complex DWPH-Hg2+ as a relay response probe could also be applied to S2− according to displacement approach. Notably, the detection limit for S2− was calculated as 23.3 nM, exhibiting that DWPH showed great potential for environmental monitoring and bioimaging. In addition, DWPH were successfully used to determine Hg2+ and S2− in living cells and zebrafish based on excellent permeability and low cytotoxicity. What's more, the gradient concentration color changes of Hg2+ and S2− were combined with the smartphone APP to obtain red–green–blue (RGB) values, thus enabling rapid semi-quantitative detection of Hg2+ and S2− without expensive instruments.